Preparation of highly-crystalline large silicon nanoparticles for high-performance lithium-ion batteries in room temperature ionic liquid systems

The reported reaction systems employed for the synthesis of nano-silicon typically involve high temperatures, costly apparatus, meticulously controlled inert atmospheres, or highly reactive reducing agents. As a result, these factors inevitably lead to substantial energy expenditure, safety risks, and intricate operational procedures. Herein, an innovative approach is presented for the synthesis of large-size and highly-crystalline nano-Si through an ionic liquid reaction system. This unique room temperature ionic liquid system effectively facilitates the internal kinetic reactions and synthesizes large-size nano-Si with primary particle sizes ranging from 63 to 155 nm by varying the reaction temperature. Remarkably, when employed as the anode material in lithium-ion batteries, the resulting nano-Si-200 without the need for carbon coating and hydrofluoric acid etching treatment exhibits exceptional long-term cycling stability, with a superior capacity retention rate of 98.8 % at 0.5 A g⁻¹ after 300 cycles. Moreover, the retention rate remains at 80.2 % while maintaining a specific capacity of 1097 mA h g⁻¹ after 700 cycles at 2 A g⁻¹, and persistently endures for 1000 cycles at 3 A g⁻¹ with a specific capacity of 962 mA h g⁻¹. This preparative system provides a new avenue for the synthesis of large nano-Si and holds promise for inspiring advancements of nano-Si in various fields.